custom will_paginate renderer

Documentation is lacking for will_paginate custom renderers:

There is no documentation how to write your own link renderer, but the source code is pretty self-explanatory. Dive into it, and selectively override methods of the LinkRenderer to adjust them to your needs.

Is there any unofficial documentation?

Found a decent blog post about custom will_paginate renderer

module ApplicationHelper
  # change the default link renderer for will_paginate
  def will_paginate(collection_or_options = nil, options = {})
    if collection_or_options.is_a? Hash
      options, collection_or_options = collection_or_options, nil
    end
    unless options[:renderer]
      options = options.merge :renderer => MyCustomLinkRenderer
    end
    super *[collection_or_options, options].compact
  end
end

and then in an initializer

class MyCustomLinkRenderer < WillPaginate::ActionView::LinkRenderer do
  def container_attributes
    {class: "tc cf mv2"}
  end

  def page_number(page)
    if page == current_page
      tag(:span, page, class: 'b bg-dark-blue near-white ba b--near-black pa2')
    else
      link(page, page, class: 'link ba b--near-black near-black pa2', rel: rel_value(page))
    end
  end

  def gap
    text = @template.will_paginate_translate(:page_gap) { '&hellip;' }
    %(<span class="mr2">#{text}</span>)
  end

  def previous_page
    num = @collection.current_page > 1 && @collection.current_page - 1
    previous_or_next_page(num, @options[:previous_label], 'link ba near-black b--near-black pa2')
  end

  def next_page
    num = @collection.current_page < total_pages && @collection.current_page + 1
    previous_or_next_page(num, @options[:next_label], 'link ba near-black b--near-black pa2')
  end

  def previous_or_next_page(page, text, classname)
    if page
      link(text, page, :class => classname)
    else
      tag(:span, text, :class => classname + ' bg-dark-blue near-white')
    end
  end
end